PyQt5: Change layout for multiple objects at once

Question

Okay, so I have a QMainWindow object that is my window and that contains several QLineEdit objects. Depending on a condition, a single QLineEdit object can change it's color (color: red if error). I'm trying to find a way to reset the color of all QLineEdit objects back to black (default) when pressing a button. Right now, I have them all in a single list and iterate through them, which is inefficient because I have ~60 QLineEdit objects.

I'm looking for a way to change the stylesheet globally for all QLineEdit objects within my window, at once.

Ui_MainWindow is a class that is automatically generated by Qt Designer and imported. I make all the changes to my class MainWindow, instead of Ui_MainWindow, as Qt Desginer tells me to.

from PyQt5.QtWidgets import QMainWindow    
from Windows.main_window import Ui_MainWindow

class MainWindow(QMainWindow, Ui_MainWindow):
    def __init__(self):
        super(QMainWindow, self).__init__()

        self.ui = Ui_MainWindow()
        self.ui.setupUi(self)

        # Input validation
        self.ui.lineEdit.textChanged.connect(lambda: self.validate(self.ui.lineEdit))
        self.ui.lineEdit_2.textChanged.connect(lambda: self.validate(self.ui.lineEdit_2))
        self.ui.lineEdit_3.textChanged.connect(lambda: self.validate(self.ui.lineEdit_3))

        # Open file button
        self.ui.pushButton_Open.clicked.connect(self.open_file_dialog)

        self.show()

    # If text meets a condition, paint it red
    def validate(self, element):
        if element.text() == 'foo':
            element.setStyleSheet('color: rgb(255,0,0)')

    def open_file_dialog(self):
       self.reset_stylesheet()
       ...

    def reset_stylesheet(self):
        ui_elements = [self.ui.lineEdit, self.ui.lineEdit_2, self.ui.lineEdit_3]
        for element in ui_elements:
            element.setStyleSheet('color: rgb(0,0,0)')

Answer 1

You could try something like this but I'm not sure how much faster it will be.

I changed the connect methods to line.textChanged.connect(self.validate) though you could change them back use element.setProperty in the validate funciton

Add the top two lines to the __init__ method.

    self.setStyleSheet('QLineEdit[validated=true]{color: rgb(255,0,0)}')
    self.lineEdits = (x for x in self.centralWidget().children()
                      if isinstance(x, QLineEdit))

# If text meets a condition, paint it red
def validate(self, element):
    if element == 'foo':
        self.sender().setProperty('validated',True)
    else:
        self.sender().setProperty('validated',False)
    self.sender().setStyle(self.style())

def invalidate(self, element):
    element.setProperty('validated', False)
    element.setStyle(element.style())
    return element


def open_file_dialog(self):
   self.reset_stylesheet()


def reset_stylesheet(self):
    tuple(map(self.invalidate, self.lineEdits))

Or you could just add

self.setStyleSheet('QLineEdit{color:#FFF};') in the reset_stylesheet() function

and

self.setStyleSheet('QLineEdit{color:#F00};') in the validate section.